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Published online before print August 26, 2005, 10.1148/radiol.2371041432
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(Radiology 2005;237:189-196.)
© RSNA, 2005

Gastrointestinal Imaging

Suspected Acute Colon Diverticulitis: Imaging with Low-Dose Unenhanced Multi–Detector Row CT1

Denis Tack, MD, PhD, Pascale Bohy, MD, Ingrid Perlot, MD, Viviane De Maertelaer, PhD, Orfan Alkeilani, MD, Stavroula Sourtzis, MD and Pierre Alain Gevenois, MD, PhD

1 From the Department of Radiology, CHU de Charleroi (CHUC), Charleroi, Belgium (D.T., P.B., O.A., S.S.); Department of Gastroenterology, Hôpital Ambroise Paré, Mons, Belgium (I.P.); Statistical Unit, Institut de Recherche Interdisciplinaire en Biologie Humaine et Moléculaire, Université Libre de Bruxelles, Brussels, Belgium (V.D.M.); and Department of Radiology, Hôpital Erasme, Université Libre de Bruxelles, Brussels, Belgium (P.A.G.). Received August 17, 2004; revision requested October 28; revision received November 17; accepted December 30. Address correspondence to D.T., Department of Radiology, RHMS Clinique Louis Caty, 136 rue Louis Caty, B-7331-Baudour, Belgium (e-mail: denis.tack{at}skynet.be).


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
PURPOSE: To prospectively compare the sensitivity and specificity of unenhanced low-dose multi–detector row computed tomography (CT) with those of contrast material–enhanced standard-dose multi–detector row CT in patients suspected of having acute diverticulitis.

MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. One hundred ten consecutive patients (40 men, 70 women; age range, 30–82 years; mean, 57 years) suspected of having acute diverticulitis underwent unenhanced multi–detector row CT with 4 x 2.5-mm collimation, 120 kVp, and 30 effective mAs, as well as contrast-enhanced standard-dose multi–detector row CT with the same parameters but with 120 mAs. All scans were independently read by four readers. Intra- and interobserver agreements were calculated with the {kappa} statistic. Contrast-enhanced standard-dose scans read by three other experts and considered together with results from colonoscopy, surgery, and pathologic evaluation were used as reference. Differences in sensitivity and specificity between readers, radiation doses, and reading sessions were investigated. Pearson exact test and logistic regression models were used.

RESULTS: Colon diverticulitis was present in 39 patients (34%) and was graded as mild in 22 patients (56%) and severe in 17 (44%). Agreement within and between readers was good to excellent. No significant difference was observed in sensitivity (P ranging from .081 to >.99) or in specificity (P ranging from .326 to >.99) for any sign or overall diagnosis between radiation doses by all readers, except wall thickening, which for one reader had a higher specificity at low dose than at standard dose (P = .025). No significant difference in misclassification was detected between doses, regardless of the reader (P ranging from .481 to >.99). At both doses, the most predictive sign for acute diverticulitis was retroperitoneal fat stranding (P < .001).

CONCLUSION: Low-dose unenhanced multi–detector row CT has a diagnostic performance similar to that of contrast-enhanced standard-dose multi–detector row CT in patients suspected of having acute diverticulitis.

© RSNA, 2005


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 
The diagnosis of acute diverticulitis is often based on a patient's history and findings at physical examination. However, because of the large variety of unspecific symptoms and signs, this approach by itself is not sufficient, and the rate of misdiagnosis approaches 34% (1–4). Consequently, for patients suspected of having acute colon diverticulitis, computed tomography (CT) has become the optimal method for diagnosis, grading of severity, and quantification of the disease resolution (5). In addition, CT is faster than other imaging techniques and enables possible alternative and/or additional diagnoses (5–7). However, CT exposes a patient to a radiation dose two to five times higher than that delivered by other standard imaging techniques used in the same setting (8,9). Further, with the recently introduced multi–detector row CT technology, repeated acquisitions, extended z-axis coverage, and thin collimations may increase the radiation dose per examination by an additional 40% compared with that with single–detector row CT (9). This is especially of concern in patients with diverticulitis. Patients with diverticulitis can be young and have a high risk of recurrence (1). These patients experience a relatively high level of radiation exposure from these examinations that is then compounded during frequent follow-up examinations, which are usually required in these young patients.

A reduction in radiation dose has already been investigated for diagnostic examinations of conditions characterized by high intrinsic contrast between structures, such as pulmonary nodule screening (10), diagnosis of ureteral stones (5,11–13), and CT colonography (14). Most recently, a reduced dose has been investigated for diagnosis of acute appendicitis. This resulted in a diagnostic performance similar to that with standard-dose CT, even without oral, rectal, or intravenous administration of contrast material (15). Colon diverticulitis, however, demonstrates low intrinsic contrast. Thus, the aim of the present study was to prospectively compare the sensitivity and specificity of unenhanced low-dose multi–detector row CT with those of contrast-enhanced standard-dose multi–detector row CT in patients suspected of having acute diverticulitis.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 References
 
From February to August 2002, 110 consecutive patients (40 men and 70 women) suspected of having acute diverticulitis who presented with acute or subacute pain in the left iliac fossa for less than 2 weeks were referred to the radiology department (at CHU of Charleroi) for CT, and all were included in the study group. These patients were 30–82 years old (mean, 57 years) and had a mean body mass index of 27.2 kg/m2 (range, 17.6–39.1 kg/m2). The study protocol was approved by our institutional review board, and written informed consent was obtained from all patients after radiation dose information, including risks from CT radiation, had been explained.

CT Examinations
Images were obtained by using a commercially available multi–detector row CT scanner (Somatom Volume Zoom; Siemens Medical Systems, Forchheim, Germany). Patients were examined while in the supine position. A 51-cm scout view was first obtained at 120 kVp and 35 mA, followed by a first helical scan with 4 x 2.5-mm collimation (ie, four detectors with 2.5-mm section thickness) at 120 kVp and 30 effective mAs. A second helical scan with the same CT parameters, but with 120 effective mAs, was then acquired and was combined with intravenous injection of 120 mL of iodinated contrast material (iobitridol, Xenetix 350 [350 mg of iodine per milliliter]; Guerbet, Aulnay-sous-Bois, France) at 2 mL per second and a start delay of 70 seconds. As defined by Mahesh et al (16), "effective mAs" corresponds to the milliampere-second value divided by the pitch, whereby pitch was defined by Silverman et al (17) as the ratio between the table feed per rotation and the x-ray beam width. Pitch factor was 1.5 and the table feed according to scanner rotation was 15 mm. The tube current was automatically modulated by an online tube current control (Care Dose; Siemens Medical Systems) during all acquisitions. All examinations were performed from the upper surface of the liver to the symphysis pubis. From the raw data of both acquisitions, 3-mm-thick transverse images were reconstructed with 2-mm increments. From each data set of 3-mm sections, we reconstructed 60 multiplanar reformations, each with a 5-mm thickness in a coronal oblique orientation parallel to the lower abdominal wall.

Effective Dose Calculation
The effective dose was simulated by means of a personal computer with commercially available software installed (CT-Expo; Medizinische Hochschule, Hannover, Germany). This software does not require phantom measurements. CT acquisition parameters, patient sex, and the scanned region as represented on a graph of the Monte-Carlo phantom model were entered into the program. For each acquisition, milliampere-second values given to the program corresponded to the ones displayed on the CT images after tube current modulation, whereby this modulation was independent to body habitus and the milliampere-second presets (18). The program calculated effective doses by taking into account scanner parameters as reported by Nagel (19) and conversion factors as reported by Zankl et al (20,21). The calculated effective doses are expressed according to the International Committee on Radiation Protection and Measurements Publication 60 (22) recommendations.

Image Analysis
Native and multiplanar images were stored on compact disks and read on a clinical workstation with three-dimensional functionalities (Wizard; Siemens Medical Systems). These images were read independently by four readers: a general radiologist (O.A.) with more than 20 years experience in reading body CT scans (reader 1); a gastrointestinal radiologist (S.S.) with more than 10 years of experience in reading abdominal CT scans (reader 2); a 2nd-year radiology resident (P.B.) (reader 3); and a gastroenterologist (I.P.) with 12 years of clinical experience but without any specific education in CT imaging (reader 4). Readers were unaware of the definite diagnoses, but they knew that the patient had presented with acute or subacute left iliac fossa pain for less than 2 weeks.

Readings were conducted in the following manner: Reconstructions from low-dose scans were read twice in two separate reading sessions, with a 2-week minimum interval between readings. Scans were presented to readers in the same patient order. One month later, reconstructions from standard-dose scans were read once by each reader. For all readings, readers were asked to record the presence or absence of colon diverticula, colon wall thickening (by means of comparison with adjacent colonic segments), retroperitoneal fat stranding, and/or abscess (air and fluid collection) in the peritoneum and/or the retroperitoneum. In addition to these items, readers were asked to give an overall diagnosis of colon diverticulitis, to grade its severity as low or high, and to suggest an alternative diagnosis, if any. As defined by Horton et al (23) and Ambrosetti et al (24), low-grade diverticulitis consisted of segmental wall thickening with inflammatory changes in the pericolic fat, whereas high-grade diverticulitis consisted of the same accompanied by abscess formation, a gaseous collection within the peritoneum and/or the retroperitoneum, and/or a fistula to adjacent organs (23,24). Exemplary images of low-grade diverticulitis are shown in Figure 1 .



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  		Figure 1a. Transverse multi–detector row CT scans (4 x 2.5-mm collimation, 120 kVp) obtained at the level of the sigmoid colon in a 41-year-old man (body mass index, 26.7 kg/m2) with acute colon diverticulitis. All readers interpreted low- and standard-dose scans as low-grade acute diverticulitis of sigmoid colon. (a) Unenhanced low-dose scan acquired at 30 mAs preset and (b) contrast-enhanced standard-dose scan acquired at 120 mAs preset show fat stranding (arrow) around the colon.

 


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  		Figure 1b. Transverse multi–detector row CT scans (4 x 2.5-mm collimation, 120 kVp) obtained at the level of the sigmoid colon in a 41-year-old man (body mass index, 26.7 kg/m2) with acute colon diverticulitis. All readers interpreted low- and standard-dose scans as low-grade acute diverticulitis of sigmoid colon. (a) Unenhanced low-dose scan acquired at 30 mAs preset and (b) contrast-enhanced standard-dose scan acquired at 120 mAs preset show fat stranding (arrow) around the colon.

 
Definite Diagnosis
A separate panel composed of two radiologists, one with 15 years (D.T.) and one with 20 years of experience in reading abdominal CT scans, and one gastroenterologist with 25 years of clinical experience considered the scans from contrast-enhanced standard-dose CT and all available clinical data from medical charts. These panelists established the definite diagnosis in consensus. They were not involved in scoring the low-dose and the standard-dose scans. The panel was also asked to grade the severity of diverticulitis as low or high and to suggest an alternative diagnosis, if any. Clinical data available from medical charts (in all patients) consisted of colonoscopy results (in 55 patients) and surgical findings (in 19 patients)—both with pathologic results (74 patients)—and the serum C-reactive protein level with a normal upper limit in our laboratory at 0.5 mg per 100 mL (in 89 patients). If the serum C-reactive protein level was lower than this threshold value and was associated with the relief of pain without antibiotic, the diagnosis of diverticulitis was excluded.

Statistical Analysis
Intrareader and interreader agreements were investigated by calculating the Cohen {kappa} statistics with asymptotic standard error (ASE) (25). Interreader agreements were assessed for both reading sessions. All {kappa} values were interpreted as proposed in the literature (26): A {kappa} value lower than 0.20 indicates poor agreement; 0.21–0.40, fair agreement; 0.41–0.60, moderate agreement; 0.61–0.80, good agreement; and 0.81–1.00, excellent agreement.

Sensitivity and specificity of each CT sign, the overall diagnosis of diverticulitis or an alternative disease, and the CT assessment of the disease severity were calculated for each radiation dose, each reader, and each reading session at low-dose. Differences in sensitivity and specificity between readers, radiation doses, and reading sessions at low-dose were investigated. All proportions were compared by using the Pearson exact test.

Logistic regressions were used to model the probability of correctly diagnosing diverticulitis as a function of the following CT signs: presence of colon diverticula, colon wall thickening, retroperitoneal fat stranding, and abscess. These logistic regressions were performed at low dose (first reading) and then at standard dose for each of the two best reproducible readers. For each of these four regressions, a stepwise method was used to determine the successive signs useful for best predicting that probability.

No correction for multiplicity for many statistical tests was performed because such a correction would have entailed an enhancement in the number of nonsignificant tests. We were interested in showing absences of differences between the different conditions compared (readers, doses), so we used the least favorable conditions.

The level of statistical significance for all tests was set at P < .05. The statistical software programs used were SPSS for Windows (release 11.5; SPSS, Chicago, Ill) and StatXact (release 5.0.3; Citel Software, Cambridge, Mass).


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 References
 
Definite Diagnosis
In 39 patients (18 men and 21 women), a definite classification of acute diverticulitis was made. All of these patients had an elevated serum C-reactive protein that normalized after specific treatment. Thirty-seven patients had positive results at colonoscopy, and in 14 patients who were treated by means of surgery, there was a pathologic diagnosis of acute diverticulitis. Among the 39 patients, 22 and 17 patients were respectively classified as having a low and a high grade of severity. Among those with high-grade diverticulitis, 14 patients had an abscess, three patients had a gaseous collection within the peritoneum and/or the retroperitoneum, and no patient had a fistula to adjacent organs.

Seventy-one patients (23 men and 48 women) were definitely classified as having no acute diverticulitis. Forty-nine of them had a normal serum C-reactive protein level and relief of pain without antibiotics. Of these 71 patients, colonoscopy results were normal in eight and demonstrated an alternative colonic disease in seven. Five patients underwent surgery, and visual inspection by the surgeon, as well as pathologic examination, revealed the absence of diverticulitis but the presence of an alternative disease (colon cancer in three patients, colon ischemia in two patients). In 22 of the 71 patients, an alternative disease was confirmed by means of favorable response to a specific medical or surgical treatment and/or by means of further diagnostic tests. Alternative diagnoses consisted of ureteric stone in five patients, ovarian cyst in three patients, inflammatory bowel disease in three patients, colon cancer in two patients, sigmoid volvulus in two patients, small bowel obstruction in two patients, colonic ischemia in two patients, abdominal wall muscle hematoma complicating coagulation disorders in two patients, and acute pancreatitis in one patient.

Intrareader and Interreader Agreements
Frequency of each sign, overall diagnosis of diverticulitis or alternative disease, and high-grade diverticulitis are listed in Table 1.


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  		TABLE 1. Frequency of Signs, Diagnosis of Acute Diverticulitis, Alternative Disease, and High-Grade Diverticulitis

 
The {kappa} values (± ASE) for intrareader and interreader agreements for each sign, for the overall diagnosis of diverticulitis or alternative disease, and for grading the severity of diverticulitis are shown in Figures 2–4. Interreader agreements for the overall diagnosis of diverticulitis were excellent among the radiologists (ie, readers 1, 2, and 3), but agreements between a radiologist and the gastroenterologist (reader 4) were only good.



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  		Figure 2. Graph shows intrareader agreement ({kappa} ± ASE) at low-dose unenhanced multi–detector row CT for signs of diverticulitis, overall diagnosis of diverticulitis, alternative diagnoses, and diverticulitis severity grading by readers 1 ({bullet}), 2 ({circ}), 3 ({blacktriangleup}), and 4 ({triangleup}).

 


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  		Figure 3. Graph shows interreader agreements ({kappa} ± ASE) at low-dose unenhanced multi–detector row CT for signs of diverticulitis, overall diagnosis of diverticulitis, alternative diagnoses, and diverticulitis severity grading. Agreements are shown between readers 1 and 2 ({bullet}), between readers 1 and 3 ({circ}), between readers 1 and 4 ({blacktriangleup}), between readers 2 and 3 ({triangleup}), between readers 2 and 4 ({blacksquare}), and between readers 3 and 4({square}).

 


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  		Figure 4. Graph shows interreader agreements ({kappa} ± ASE) at standard-dose contrast-enhanced multi–detector row CT for signs of diverticulitis, overall diagnosis of diverticulitis, alternative diagnoses, and diverticulitis severity grading. Agreements are shown between readers 1 and 2 ({bullet}), between readers 1 and 3 ({circ}), between readers 1 and 4 ({blacktriangleup}), between readers 2 and 3 ({triangleup}), between readers 2 and 4 ({blacksquare}), and between readers 3 and 4({square}).

 
Diagnosis Performance
Results for sensitivity and specificity of each CT sign, of the overall diagnosis of diverticulitis or alternative disease, and of the disease severity calculated for each radiation dose, each reader, and each reading session at low radiation dose are listed in Tables 2 and 3. Comparisons of these values within readers, radiation doses, and reading sessions at low radiation dose are summarized in these tables.


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  		TABLE 2. Sensitivity of Findings and Comparison among Readers and Radiation Doses

 

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  		TABLE 3. Specificity of Findings and Comparison among Readers and Radiation Doses

 
For signs that showed significant overall differences in sensitivity or specificity, we looked for further differences according to the dose, the reader, and the reading session. Between the doses, no statistically significant difference was observed in sensitivity (P ranging from .081 to >.99) or in specificity (P ranging from .326 to >.99) for any sign by any readers, except wall thickening, which showed a higher specificity at low dose than at standard dose for reader 3 (P = .025).

Results of comparisons of sensitivity and specificity between readers at low dose and standard dose are listed in Table 4. Between reading sessions at low dose, no statistically significant difference was observed in sensitivity (P ranging from .125 to >.99) or in specificity (P ranging from .292 to >.99) by any readers for any sign, but wall thickening was detected by reader 3 (P = .025 and .002, respectively, for sensitivity and specificity).


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  		TABLE 4. Comparison of Sensitivity and Specificity between Readers at Low-Dose and Standard-Dose CT

 
Logistic regression models were applied to the results from the two readers who had the highest rate of correct classifications of acute diverticulitis (readers 2 and 3), compared with the method of reference. At both radiation doses, the most predictive sign was retroperitoneal fat stranding (P < .001), followed by presence of colon diverticula (P < .001), at both radiation doses and for both readers. The first two variables were identical and were elicited in the same order in each model (P < .001) and were followed by the presence of colon diverticula and colon wall thickening.

Misclassifications Compared with the Definite Diagnosis of Diverticulitis
The numbers of misclassifications in assessment of overall diagnosis of diverticulitis and alternative disease are listed in Table 5. Two of the four readers (readers 2 and 3) correctly diagnosed acute diverticulitis in all 39 patients from scans at both low- and standard-dose multi–detector row CT. Among these 39 patients, there were significant differences in number of misclassifications between reader 1 and reader 2 (P = .025) and 3 (P = .025) at 30 mAs but not at 120 mAs (P = .067 for both).


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  		TABLE 5. Numbers of Misclassifications in Assessment of Overall Diagnosis of Diverticulitis and Alternative Disease

 
Among the other 71 patients (ie, no definite diagnosis of acute diverticulitis), there were significant differences in number of misclassifications between reader 2 and reader 4 (P = .028) at standard dose but not at low dose (P = .096).

For each reader individually, there was no significant difference detected between low and standard dose (P ranging from .481 to >.99).

Misclassifications Compared with Definite Diagnosis of Alternative Diseases
The frequencies of each alternative disease from each reader at standard-dose and low-dose CT are listed in Table 6. Among patients with definite diagnosis of alternative disease, there were significant differences in number of misclassifications between reader 1 and reader 4 (P = .021). Among patients without definite diagnosis of alternative disease, there was no significant difference between readers, regardless of the dose (P > .99).


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  		TABLE 6. Frequency of Alternative Diagnosis from Each Reader at Low-Dose and Standard-Dose CT

 
For each reader individually, no significant difference was detected between doses (P ranging from .183 to >.99).

Effective Radiation Dose
The mean height of the scanned region was 38 cm in men and 33 cm in women. The mean effective dose was 1.2 mSv in men and 1.6 mSv in women.


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
References
 
Results of the present study showed that for patients suspected of having acute colon diverticulitis (a) sensitivity and specificity were similar, regardless of dose, (b) predictive values of all signs considered were not affected by dose, (c) interobserver agreements ranged from good to excellent, regardless of dose, and (d) CT has potential to depict alternative disease. The final diagnosis was achieved without intravenous injection of iodinated contrast medium and with an effective radiation dose corresponding to that of a conventional radiographic examination of the abdomen with three views (9,11,15). The low-dose technique results in a dose reduction of 75%–90% compared with that of standard-dose abdominal multi–detector row CT (8,9,11,15).

Several aspects of the current investigation deserve further discussion. First, in previous studies fat stranding has already been reported as the most predictive sign for the diagnosis of acute appendicitis at both standard- and low-dose multi–detector row CT (15) and for diagnosis of acute colon diverticulitis at standard-dose CT (27,28). In our study, this sign was also the most predictive indicator for acute colon diverticulitis, at both low and standard radiation doses. In the present study, colon wall thickening was not predictive of acute diverticulitis, probably because this sign is also present in colon diverticulosis and reflects the muscular layer thickening (29).

Second, dose reduction does not affect ability to grade severity. Results of this study revealed that low-dose multi–detector row CT enabled one to correctly assess the presence of abscess and air collections distant to the colon—the two most predictive signs of recurrence (30).

Third, in the present study, as well as in previous ones (11–13), the lower dose was not responsible for any significant loss in diagnostic performance regarding acute colon diverticulitis and alternative diseases. This is observed for both experienced radiologists and for less-experienced readers, such as a 2nd-year radiology resident and an experienced gastroenterologist who has no specific education in CT imaging.

Last, results of this study showed that the diagnosis of acute left colon diverticulitis may be achieved without a contrast-enhanced enema. Although enema is generally considered to be a safe procedure (5,23), it is not completely without complications, such as colon perforation, as recently reported by Gayer et al (31). In addition, enema leads to longer duration of the CT procedure and additional costs.

The present study might have some limitations. First, the study addressed two simultaneous variables. The influence of dose reduction was not investigated without the use of contrast material. To separate these two items, two additional multi–detector row CT scans should have been acquired: one at standard dose without contrast material and one at low dose with iodine injection. However, in doing this the radiation dose per patient would have been ethically unacceptable. Consequently, it was our consensus that both issues could be investigated together without impairing the clinical implications of this study, thus sparing unnecessary radiation exposure. Further, a protocol with four CT acquisitions would have resulted in a huge increase in the number of images to read and may have influenced reviewers' performances. However, as we did not detect any significant difference between standard-dose multi–detector row CT with contrast material and low-dose multi–detector row CT without contrast material, there is no reason to believe that differences between contrast-enhanced and unenhanced low-dose CT or between contrast-enhanced and unenhanced standard-dose CT might have reached statistical significance separately.

A second limitation was the low proportion of patients with a body mass index greater than 35. There was also an absence of extremely obese patients (body mass index, >40). In such patients, image noise may be of huge importance, and, as suggested by Katz et al (32), low-dose images with acceptable noise may be obtained with 60 mAs. Since the effective dose in larger patients is lower than that in smaller ones—absorption of x-rays is divided by two, while abdominal diameter is increased by 4 cm—the use of 60 mAs presets may not correspond to higher effective radiation doses than with 30 mAs presets in normal and underweight patients (33).

Third, we included patients suspected of having acute colon diverticulitis, independently of age-related risk for radiation-induced cancer. Even if low-dose multi–detector row CT delivers 1/10 of the radiation dose delivered by a standard multi–detector row CT examination, elderly patients will not benefit from dose reduction, as radiation accumulation from repeated exposure is not likely to happen on account of their additional life expectancy (34). Rather, these patients may benefit more from absence of iodine contrast material injections and enema than dose reduction.

In conclusion, results of the present study suggest that, in patients suspected of having acute colon diverticulitis, low-dose unenhanced multi–detector row CT has a diagnostic performance that is similar to that of contrast-enhanced standard-dose multi–detector row CT.


   ACKNOWLEDGMENTS
 
We thank Alain Van Muylem, PhD, for figure preparation.


   FOOTNOTES
 

Abbreviations: ASE = asymptotic standard error

Authors stated no financial relationship to disclose.

Author contributions: Guarantors of integrity of entire study, D.T., P.A.G.; study concepts/study design or data acquisition or data analysis/interpretation, all authors; manuscript drafting or manuscript revision for important intellectual content, all authors; approval of final version of submitted manuscript, all authors; literature research, D.T., I.P.; clinical studies, D.T., P.B., I.P., O.A., S.S.; statistical analysis, V.D.M., P.A.G.; and manuscript editing, D.T., V.D.M., P.A.G.


   References
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 References
 

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